In polymerization processes of producing polycarbonate, a filter is often used after polymerization to remove contaminants such as gels, agglomerated additives, and carbonized polymer particles from the polycarbonate. The successful removal of such contaminants can be especially important in producing polycarbonates with good optical properties.
When a change in pressure across the filter reaches a certain level, the filter needs to be replaced. Replacement entails shutting down the system, and replacing the spent filter with a new filter. This process can take several hours to properly shut down the system, remove the spent filter, properly align the new filter, and restart the system. In an attempt to expedite the process, the alignment of the new filter is often rushed. This can result in a misaligned filter which will likely become damaged. A damaged filter, even having just a small break, that is not easily detectable with, for example, a pressure sensor, can disadvantageously result in the presence of particulates in the product polycarbonate. Consequently, the filter will again need to be replaced.
Clearly, filter replacement in any polycarbonate process is a source of reduced efficiency and hence an area for improvement. This is particularly the case in larger production polycarbonate processes as the impact of each hour of down time is more significant. Many typical polycarbonate process plants have a capacity of less than or equal to 35 tons per day. Replacement of a filter in such a plant can result in productivity loss of 2 to 4 hours of production. In larger polycarbonate plants, the productivity loss can be in the order of tenths of tons.
Improved methods for changing a filter in a polymerization process (e.g., an interfacial polymerization process) are needed.